1. Field of the Invention
The invention is directed to a hearing aid system as well as to a method for the setting of a hearing aid system having at least a first and a second hearing aid device that at least respectively comprise at least one input transducer for the pick-up of an acoustic input signal and conversion thereof into an electrical signal, a signal processing unit for processing the electrical signal and an output transducer for converting the electrical signal into an output signal, and between which a signal path for data transmission is provided.
2. Description of the Related Art
Directional hearing is the ability of a person to distinguish the direction in which a sound source is located. When a sound source is not frontally located in front of or behind the person, a difference in transit time between the two ears and, thus, a time difference with which the ears perceive a sound wave coming from a direction necessarily derives due to the finite propagation speed of sound. When, for example, a sound comes from the right from the point of view of the person, this reaches the right ear a fraction of a second sooner than the left ear. This time difference is far shorter than the person can consciously recognize. The effect arises due to an automatic integration process in the acoustic nerve system.
In addition to the time difference, a difference in the volume with which the ears perceive a sound that comes from one side derives. A sound source at one side of the head conveys a somewhat louder tone to the ear at this side. This minimal difference in the volume also suffices so that the sound source can be localized at the left or right from the point of view of the person.
A loss of directional hearing often occurs given binaural hearing aid coverage. The particular reason for this is that, dependent on the hearing situation that the respective hearing aid device detects, the signal processing of the two hearing aid devices can comprise different steps. Further, the hearing loss for a hearing aid user is usually of a different degree in the two ears. Accordingly, the settings of the hearing aids for compensating the hearing loss of the respective ear are also differently set.
Different settings of the signal processing of the two hearing aids, however, usually result in different signal transit times within the hearing aid devices. An unnatural phase shift of an acoustic input signal that is important for directional hearing therefore occurs. As initially mentioned, the transit time of a sound signal between the two ears is of great significance for directional hearing, in addition to the difference in the volume. Even slight changes of this natural transit time shift as caused, for example, by different signal transit times within the hearing aid devices, can therefore lead to a loss of directional hearing.
For solving this problem, it is known to process the acoustic signals picked up at the two ears in a common, central signal processing device. In addition to two hearing aids worn at a respective ear, U.S. Pat. No. 5,479,522 therefore provides an additional processor unit that, for example, can be implemented as a chest device or wrist watch. The acoustic signals picked up at the two ears pass through the same signal processing steps, so that the phase relationship between the two signals is preserved.
U.S. Pat. No. 5,434,924 discloses that the signal processing given binaural coverage be essentially implemented in only one of the two hearing aid devices. To this end, the signals received at one ear are transmitted onto the hearing aid of the other ear, are processed in common thereat and then supplied to both ears (a master-slave solution).
The first-cited solution has the disadvantage that a further assembly is needed and the hearing aid user now requires three devices instead of two, which means a considerable limitation of the wearing comfort, maintenance and manipulation. The second solution requires that the entire signal processing must be performed by a single signal processing unit at only one side. Whereas adequate space is present in the solution with a third device in order to provide a correspondingly powerful signal processing, the space in a hearing aid situated at the ear is limited. A master-slave solution with two differently fashioned hearing aid devices must therefore necessarily have less of a computational capacity than would be available given utilization of both hearing aid devices.
Another approach to solving this problem is to transmit the incoming sound signals at the hearing aid devices of both sides to the respectively other device and processing both signals at each side. In this way, the acoustic signals picked up at the two ears undergo the same steps of the signal processing in common and therefore automatically experience the same signal delay. This approach proceeds, for example, from International Patent Publications WO 97/14268 and WO 99/43185. Although the transmission of the microphone signals of both sides of a binaural hearing aid system to the respectively other side and the simultaneous processing of both signals at both sides solves the problem of a transit time difference, it is subject to the same limitations as the master-slave approach.
Another significant disadvantage of all of these solutions is that they all require the transmission of large quantities of data. This causes a substantial use of time, space and energy, and represents a considerable disadvantage, particularly given wireless data transfer as offered in the present state of the art.
European Patent Document EP 0 941 014 A2 discloses a hearing aid system with a first and a second hearing aid, whereby control signals are generated by actuating an operating element at the first hearing aid and are transmitted onto the second hearing aid. The simultaneous setting of both hearing aids is thereby effected by the actuation of the operating element at one of the hearing aids.
German Patent Document DE 100 48 354 A1 discloses a method for the operation of a hearing aid system wherein characteristic values of the acoustic field are transmitted from one hearing aid to the other. This can thereby be a matter of signal levels.
German Patent Document DE 197 04 119 C1 discloses a hearing aid wherein a signal transmission from one hearing aid to the other is undertaken via light guides. Control signals can thereby be transmitted.